Structure, magnetic and optical properties of Sr3RE2(Ge3O9)2 cyclogermanates (RE = La–Gd). Issue 17 (12th April 2018)

• Record Type: Journal Article
• Authors: Chufarov, Alexander Yu.; Lipina, Olga A.; Surat, Ludmila L.; Melkozerova, Marina A.; Baklanova, Yana V.; Enyashin, Andrey N.; Tyutyunnik, Alexander P.; Kellerman, Dina G.; Zubkov, Vladimir G.
• Is Part Of: CrystEngComm. Volume 20:Issue 17(2018)
• Page Start: 2404
• Page End: 2412
• Publication Date: 2018-04-12
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c8ce00005k
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : A new group of cyclogermanates has been characterized using XRD, DFT calculations, photoluminescence spectroscopy and magnetic study. Abstract : A new series of Sr3 RE 2 (Ge3 O9 )2 ( RE = La, Pr, Nd, Sm, Eu, Gd) cyclogermanates has been prepared using an ethylenediaminetetraacetic acid assisted route. The powder XRD study reveals that the compounds crystallize in the monoclinic space group C 2/ c, Z = 4. A decrease in the crystal radius of RE 3+ ions in Sr3 RE 2 (Ge3 O9 )2 ( RE = La–Gd) causes a morphotropic phase transition followed by a step-like change of the lattice parameters. The transition is accompanied by internal reorganization, including the redistribution of rare earth and strontium ions among three symmetry independent Sr/ RE sites, a conformation change of [Ge3 O9 ] 6− rings and a variation of Sr/ RE (2) atom coordination from seven-fold to nine-fold. Density functional theory calculations reveal that Sr3 RE 2 (Ge3 O9 )2 compounds are indirect bandgap materials with a band gap around 3.0 eV. The magnetic property measurements indicate that Sr3 RE 2 (Ge3 O9 )2 ( RE = Pr, Sm, Gd) are Curie–Weiss paramagnets up to 2 K. For Sr3 Eu2 (Ge3 O9 )2 an anomaly of magnetic susceptibility is found at about 60 K. A photoluminescence study of the Sr3 Sm2 (Ge3 O9 )2 and Sr3 Eu2 (Ge3 O9 )2 samples reveals an emission in the visible spectral range, corresponding to the characteristic 4f–4f transitions in rare earth ions.